Day Light Factor in Office Spaces



Day illuming admitted into constructing through “holes” in external cloth ( Windowss, roof visible radiations, etc. ) which in adverse climes by and large incorporate glass or an alternate transparent stuff to heat loss.

The energy efficiency and sustainability became progressively of import issues in the field of architecture. Often day-lighting is recognised as a cardinal scheme in cut downing the energy ingestion by cut downing sum of electrical lighting in a edifice. And even, twenty-four hours lighting is besides known for holding its positive effects on human wellness and productiveness. So by all these, the energy criterions and green edifice evaluation systems have strongly recommended that interior decorators incorporate twenty-four hours illuming schemes into edifice design. However, this recommendation is often ignored due to the complexness in following twenty-four hours illuming design and due to the ocular uncomfortableness caused by the inordinate sunshine incursions and Sun blaze.

Many yearss illuming analysis have been developed and used by pupils, interior decorators and advisers. From physical modeling to computing machine based simulations, analysis methods are used to foretell the public presentation of twenty-four hours illuming systems before a edifice is utilizing all these methods, we can mensurate or cipher assorted values like illumination degrees. However it is non easy to acquire accurate predictable or frequently even fiting values between techniques due to variance in variables and besides due to the sky choices.


Day lighting is a extremely cost-efficient agencies of cut downing the energy for electrical lighting and chilling. But architecture instruction frequently reduces the facet of twenty-four hours illuming to attention-getting effects on frontages and barely discusses its possible effects – non merely on cost, but wellness, wellbeing and energy.

The light affairs will research the frequently undiscovered facets of twenty-four hours lighting and present cardinal schemes for you to break integrated twenty-four hours illuming into design: from optimising constructing orientations to taking interior surface qualities that achieve the right coefficient of reflection. These stairss can significantly cut down your investing every bit good as operating costs. And while these schemes will surely catch the involvement of economically oriented clients, you will shortly detect that twenty-four hours illuming can make so much more.

The chief survey of this paper is to understand the kineticss of twenty-four hours light factor in relation to edifice infinites and to understand twenty-four hours visible radiation as a design component. The development and effects of twenty-four hours light and its factor in office edifices.


Lighting degrees in a edifice infinite are typically measured in foot-candles or lx. Light from electrical visible radiations is reasonably changeless so exact degrees of lighting can be obtained through the choice and layout of light fixtures. When it comes to twenty-four hours lighting, the light beginning is the sky vault which is outside the edifice s it becomes necessary to put in glassy gaps to acknowledge equal daytime to run into infinite demands. Planing for exact degrees of visible radiation from twenty-four hours visible radiation is hard since the light beginning is invariably altering depending on clip of twenty-four hours and conditions conditions. Alternatively of ciphering exact degrees of visible radiation ( foot tapers or lx ) in a given infinite from daytime, a daylight factor was created to mensurate comparative visible radiation degrees.

Day light factor:

The construct of daylight factor ( DF ) was developed in the United Kingdom in the early 20Thursdaycentury. Day light factors are used in architecture and edifice design in order to measure the internal natural lighting degrees.

Daylight factor is defined as the ratio of the internal illumination at a point in a edifice to the unshaded, external horizontal illumination under a CIE cloudiness sky ( Moon and Spencer 1942 ) . The chief connotation of utilizing this type of ratios instead than absolute values, was to avoid the trouble of holding frequent and frequently terrible fluctuations in the strength of twenty-four hours illuming ( Waldram 1909 ) . In the beginning, sky factors were used to cipher the twenty-four hours light illumination from the sky dome to a peculiar point in the edifice. Later on, the sky factor was evolved into the daylight factor, as the visible radiation reflected from external obstructors, visible radiation from the glazing and internal refelectances were added every bit good ( Waldram 1950 ) .

Day light factor is the ratio between indoor illumination and out-of-door illumination. It can be measured for a specific point or for an norm of a infinite. The undermentioned expression shows how to cipher twenty-four hours light factor from illumination degrees.

DF = 100 * Tocopherolin/ Tocopherolext


DF= twenty-four hours light factor

Tocopherolin: illumination due to twenty-four hours illuming on the indoor working topographic point

Tocopherolext: illumination out-of-doorss on a unobstructed horizontal plane.

Daylight reading at a mention point in a room can be made up of three constituents:

Sky constituent– the visible radiation received straight from the sky

Externally reflected constituent– the visible radiation received after contemplation from the land, edifice or other external surface and

Internally reflected constituent– the visible radiation received after being reflected from the surfaces inside a edifice.

All these three constituents need to be accounted for to find the twenty-four hours light factor. Day illuming factor was used to obtain the lower limit lighting demands, but it does non gives the thought of good twenty-four hours illuming. Even though the twenty-four hours illuming factor was used most widely to mensurate twenty-four hours lighting and for bulk of practicians, the consideration of twenty-four hours light Begins and terminals with twenty-four hours light factor ( Nabil and Mardaljevic 2005 ) . For the last 50 old ages, this design pattern has mostly remained undisputed with a few noteworthy exclusions ( Kendrick and Skinner 1980 ; Tregenza 1980 ) . So it is widely accepted, quantitative public presentation step for twenty-four hours lighting.

Day light factor has besides got different back uping qualities for the design use in the edifices. Depending on the edifice designs, the twenty-four hours light factors have the capacity to act upon the design picks. Coming to the different facets where the twenty-four hours light factor can impact the edifice design were similar, the geometry of the edifice, environing landscapes and environing edifices. Not merely the external belongingss, due to the twenty-four hours light factor, there a considerable affects in the inside of the edifices besides. They are like the coloring material, coefficient of reflection, transmission, diffuseness, secularity, etc. , have an impact on the twenty-four hours light factor.

In general, the daylight factor steps are intuitive and easy to pass on. To cipher the twenty-four hours light factor, there are a figure of methods bing. They range from simple computations to the BRE split flux method to progress computation techniques based on radiosity ( Lighting Analysts Inc. 2006 ) , Lumen Designer ( Light Technologies Inc. 2006 ) and/or Raytracing ( Ward and Shakesphere 1998 ) . Using glow, for any geometry of edifice and any type of stuff, we can cipher the twenty-four hours light factor.

The twenty-four hours light factor can besides hold the influence on twenty-four hours light planing in the peculiar edifices. Some signifier giving characteristics, which are by and large accompanied with the good twenty-four hours visible radiation, were influenced. Like the high window- caput highs, high ceiling coefficient of reflection, big frontages, wall coatings, narrow floor programs, high transmission glazing, sky light gaps, etc.

If we go for the “the more the better” attack, the maximal twenty-four hours light perforating into the edifice in a to the full glazed edifice will be more. We can hold the adequate twenty-four hours lighting, but frequently those constructing exhibit comfort and energy related jobs. By and large these are conditions which we see in commercial edifices.

There are few restrictions of the twenty-four hours light steps. They are ; Design recommendation based on the twenty-four hours light factor will be same for all types of facade orientations. Day light factor for all types of edifice locations will be same. Daylight factor does non see the season, clip of the twenty-four hours, variable sky conditions. Actually this bears really of import effects. Day light factor can non assist to forestall the blaze schemes for different facade orientations, even though the job of blaze is most outstanding.

Day light factor in office infinites:

A twenty-four hours light factor of 2 is a typical degree one would desire to accomplish for an office infinite. It assumes that 2 % of the entire visible radiation that is outside the edifice ends up on the working plane or desktop. Assuming an mean out-of-door illumination of 2500 pes tapers and a twenty-four hours light factor of 2 % the indoor illumination on the desktop would be 50 foot tapers.

2 % ten 2500 pes tapers = 50 pes tapers

Other typical twenty-four hours light factors for assorted infinites are:

Assorted infinites

Day light factor

Discussion groups


Residential life room


Residential kitchen


Office – item work


Office – outlining


Office – corridors


Schools – schoolrooms


Schools – art suites


Hospitals – wards


Hospitals – waiting suites


Sports installations


Warehouse – majority storage


Warehouse – medium size storage


Warehouse – little point storage


Calculating a twenty-four hours light factor based on the edifice design includes window/skylight sizes, overhangs/light shelves, glass types, and exterior/ interior refelectances can go really complex. A simple regulation of pollex to come close the twenty-four hours light factor for twenty-four hours lit infinites utilizing perpendicular Windowss is

D = 0.1 tens PG


Calciferol= daytime factor

PG= per centum of glass to floor country.

For illustration, a 1000sft office infinite has 200sft of Windowss, and so the twenty-four hours light factor will be

DF = 0.1 x ( 200/1000 )

= .02 or 2 %

The twenty-four hours light factor degrees can be loosely classified into three classs:

Under 2

Between 2 and 5

Over 5

Not adequately illume

Adequately lit

Well lit

Room looks glooming under twenty-four hours light entirely

Artificial lighting may be used partially

Artificial illuming by and large non required except at morning and twilight

Artificial lighting will be required

But blaze and solar addition may do jobs

Daylight factor contours:

The twenty-four hours light factor inside a room will change harmonizing to place. Day light factors are frequently given as working plane contours. Tall windows supply deeper twenty-four hours light incursion, while multiple Windowss provide more even twenty-four hours light distribution.

Appraisal of twenty-four hours light factors:

The twenty-four hours light factor inside an bing edifice can be measured straight utilizing a photometer which gives a direct reading of the twenty-four hours light factor.

In the design phase, twenty-four hours light factors can be predicted utilizing:

  • Design tabular arraies ;
  • Waldram diagram ;
  • Computer plans ;
  • Scale theoretical accounts ;
  • Day light factor protractors.

Day light factor analysis:

In malice of the twenty-four hours light factor popularity as an index of twenty-four hours light public presentations, daylight factor has some serious restrictions.

  • Day light factor doesn’t take consideration, the location of the edifice.
  • DF can non stand for the alteration in illumination degrees indoors, due to the temporal fluctuations of the sky luminosity.
  • The orientation of the frontage of the edifice has no consequence in twenty-four hours light computation.
  • Da Y light factor doesn’t buttocks blaze caused by the twenty-four hours lighting.
  • Glare is a major issue necessitating careful considerations during the design phase.
  • Day light factor is non specific about the clime.


Light is every bit much a “material” for edifice as the rocks, bricks, and other constituents used in building ; for, although there would be no wall without its structural constituents, the wall has no existent being for us unless it corresponds to a animal feeling, gained with our eyes and substantiated with our heads.

  • Derek Phillips

Natural visible radiation is recognized and varied for the qualities that it offers. Man’s faith, wellness and civilization has immense positive impact due to twenty-four hours lighting, since ages. The demand for natural light in insides has been investigated by illuming applied scientists, doctors and psychologists for several centuries, and therefore had a profound consequence on twenty-four hours lighting, the scientific discipline of natural light. Research on the effects of the want of visible radiation, the demand for position and effects on biological procedures have confirmed the factual bases for this demand.

Features of Natural Light:

Natural visible radiation that enters any room consists of two basic parts, viz. direct sunshine ( sunstroke ) and diffused fanlight.Roger Neal Goldstein in his Research on Natural Light in Architectural Designprovinces that by carefully pointing a window or a roof-light one can let for the incursion of both the elements of natural visible radiation, if desired.

Harmonizing toMillet ( 1996 ) ,the aglow consequence of all light beginnings depends on four factors:

  1. The Source ( its strength, its directional features, its coloring material )
  2. The Geometry ( its relationship between the beginning and the receiving system or having surface )
  3. Different Surfaces inside the Space ( The surfaces that receive and modify visible radiation, going secondary visible radiation beginnings in themselves by reflecting, airting and coloring visible radiation ; and the individual who views the beginning and lighted surfaces as he or she moves about. )
  4. Motion and Visual Perception of the Observer.

He besides declares that by detecting how light behaves, we can work with it to uncover architecture.

THE Beginning:

Harmonizing to Millet ( 1996 ) , “Each peculiar topographic point has its visible radiation. Light showing topographic point encompasses two distinguishable facets:

  • The topographic point itself, its physical characteristic and features that determine how it differs at any given minute from any other topographic point and
  • The peculiar set of alterations that take topographic point within it over clip, making typical forms of diurnal and seasonal alterations.

Sukhtej Singh Gill in his paper on the Study of the Characteristics of Natural Light in Selected Buildings by Le Corbusier, Louis. I.Kahn and Tadao Ando references that “these significances change the manner light interacts with the built environment.”

“ The window is a major constituent of the spacial record between interior and outside. With its size relation to the solid wall, it determines the way in which attending is focused. With its inside informations, it defines the passage between the room and landscape. ” ( Millet 1996, p. 96 )

It is in this passage of natural visible radiation from exterior to the inside that a infinite is transformed and its character is defined.


The strength of visible radiation is judged based on the perceptual experience of the objects it tends to foreground. Lam ( 1977 ) states that “ Percepts of the aglow environment ever include an affectional constituent an appraising or emotional response to the sensed province of personal businesss. ”

Opinions in a infinite, such as visible radiation or dark, bright or glooming, interesting or dull, sparkle or blaze, depend on whether or non the aglow environment meets our outlooks and satisfies our demands for ocular information by stressing what we want or need to see instead than the existent luminosity degrees in a infinite.

Directional Feature:

The directional features of natural visible radiation are defined out of the motion of the Sun across the sky. The deepness shadows and the contrast between two surfaces are born out of the directional features of the beginning of natural visible radiation one time interrupted by a physical plane or boundary. These are associated with the character of a infinite and aid to pull a meaningful relation with the beginning at all times of a twenty-four hours, month or season of a twelvemonth.

Tannizaki ( 1997 ) describes that the beauty of a Nipponese room depends on a fluctuation of shadows, heavy shadows against light shadows.

Light is an unerasable portion of our experience of life. It helps us understand the overall deepness of the scene by showcasing the difference between the bright and the dark.


The usage of colour can change the perceptual experience of a infinite. Lighter colourss reflect more light and the room appears to be of a greater size. When painted with dark colourss that tend to absorb most of the light falling on the surface, the same room appears much smaller in size. The visible radiation that filters through a coloured glass can alter the chromaticity of the base colour of the surface on which it falls.

Apart from this, natural visible radiation alterations in colour as the instance is when comparing the forenoon, afternoon or flushing visible radiation from the Sun, but this alteration is compensated by our outlook in the manner we perceive the same infinite at different times of a twenty-four hours.

Harmonizing to Philips ( 2004 ) , “ the experience of natural colour, for whilst the physical colour of our universe as experienced in daylight changes from twilight to click, the alterations are portion of our experience ; we compensate automatically, a white wall appears a white wall even if in the eventide it may be warmer, or is coloured by sunshine, or altered by cloud formations… . it is the colour we regard as natural ” .


Light is non perceptible without signifier and frailty versa says Sukhtej Singh Gill in his paper “ The Study of Characteristics of Natural Light in Selected Buildings Designed by Le Corbusier, Louis. I. Kahn and Tadao Ando ” .

He quotes Millet ‘s statements that “ Natural visible radiation that renders signifier seeable is ever altering, but we perceive the signifier as stable due to out perceptual procedure… . Shadows aid in the perceptual experience of the signifier and the spacial deepness… Extreme brightness or darkness can fade out a signifier as they tend to film over the inside informations and befog the soundness of a stuff… Silhouetting is one of the ways in which visible radiation from the roof glazing can uncover the construction. ”


Research identified benefits of daytime, sunshine every bit good as position for people’s wellness and


  • Peoples believe that working under natural daytime is better for wellness and wellbeing than electric Light( Veitch et al. , 1993/1996 )
  • Less asthenopia( Cowling et al. , 1990 ) ,higher productiveness( Visher 1989 ) ,more effectual acquisition( Heshong et al 1999 )
  • Daylight is better for psychological comfort, for office visual aspect and pleasantness, for general wellness, for ocular wellness, and for color visual aspect of people and trappingss( Heerwagen et al.,1986 )
  • Having a window, or holding entree to daylight, improves satisfaction with illuming( Veitch et al.,2003 )
  • In deep on the job infinites people have a strong penchant for being near the Windowss( Christoffersenet al. , 1999 )


  1. A Study of the Natural Light In Selected Buildings Designed by Le Corbusier, Louis. I. Kahn and Tadao Ando by Sukhtej Singh Gill ; 2006
  2. Natural Light in Architectural Design: Component and Determinant by Roger Neal Goldstein ; MIT ;1976
  3. Day light benefits in wellness attention edifices, by prof. DTG Strong.
  4. hypertext transfer protocol: //
  5. Natural light presentation, by kjeld johnso.
  6. Health and Light, by John Nash 1973.
  7. Daylighting controls (hypertext transfer protocol: //
  8. hypertext transfer protocol ; //
  9. daylight factor versusdaylihgt handiness in computer-based daylihgting simulations by Karen Kensek and Jae Yong Suk